Note: Descriptions are shown in the official language in which they were submitted.
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1 BACKGROUND OF THE INVENTION
This invention relates to stencilling, and
more particularly to stencilling apparatus having a
dual function flow-coater and -fluid scoop adjacent to
and cooperative with the squeegee.
In the performance of stencilling operations
using a stencil screen and a squeegee, a coating or layer
of ink or other stencil fluid is typically placed on the
screen such that relative movement between the screen
and squeegee forces some of the fluid through the screen
interstices onto the underlying stock. To assure an
effective amount of fluid being forced through the screen,
an excess of fluid is coated on the screen. During the
stencilling stroke, the excess is pushed ahead of the
squeegee to the end of the stencil and stencil frame where
it accumulates after repeated stencilling strokes. The
liquid carrier of the accumulated fluid tends to evaporate,
causing the remaining solids to dry up and build up
disadvantageously. While stencilling apparatus has been
developed wherein this problem is not encountered, by
the use of a submersible element, it is sometimes desir-
able to employ a conventional, nonimmersible squeegee,
e.g. on a stencil press having a cylindrical stock support
drum.
SUMMARY OF THE INVENTION
The present invention effectuates stencilling
apparatus wherein excess fluid pushed ahead of a squeegee is
uniquely scooped up at the end portion of the stencilling
stroke. This occurs with elevation of the squeegee while
the stencil is still advancing.
A trough-type scoop parallel to and spaced behind
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1 the squeegee is pivotally actuated to sweep through a
scooping motion from a first position at which an edge of
the scoop serves as a flow coater a controlled spacing above
the stencil, through the pivotal scooping motion, to a
second position at which ~he scooped fluid is retained for
the return stroke.
The apparatus can be combined with a conventional
squeegee, without excessive expense, to minimize build-up at
the end of the stencil.
These and other features, advantages and objects
of this invention will be apparent upon studying the follow-
ing specification in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a fragmentary perspective view of the
novel apparatus;
Fig. 2 is a fragmentary perspective view of the
apparatus in Fig. 1, viewed from directly above;
Fig. 3 is an enlarged sectional elevational view
of a portion of the apparatus in Figs. 1 and 2;
Fig. 4 is a fragmentary enlarged elevational view
of the apparatus in Fig. 3, viewed from the righthand side
of the apparatus as set forth in Fig. 3;
Fig. 5 is a schematic diagram showing stencilling
with the apparatus; and
Fig. 6 is a schematic diagram sho~ing scooping
action for the return stroke.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The assembly 10 depicted in the drawings includes
several conventional stencil press components such as a
support frame subassembly 12 (part of which is depicted)
upon which is rotationally suspended a support cylinder 14
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1 to form a peripheral stock support surface. This
cylinder preferably contains conventional vacuum ori-
fices around its peripheral stock support surface for con-
trolled retention of sheet or web stock during the
stencilling operation. This conventional cylinder is
rotated through a controlled arc in a conventional manner
by a ring gear 16 (shown in phantom in Fig. 1). Gear
16 intermeshes with a conventional gear rack 18 extending
longitudinally of the machine and interconnected with
the conventional stencil screen frame 17 to reciprocate
the frame and any stencil screen thereon back and
forth over the crest of the cylinder for the stencilling
and return strokes. Gear 16 is driven through a suit-
able linkage by a power source in a conventional manner.
Positioned above the crest of cylinder 14 is
a squeegee subassembly 20 coaxial to the cylinder. It
includes a transverse mount 22, the ends of which are
on a pair of supports 24 vertically movable in a lifting
and lowering action by conventional mechanism. Sus-
pended beneath the squeegee mount is a pair of housing
elements 26, between which the squeegee blade 28 is
suspended. The opposite front and rear faces of blade
28 may be reinforced by a pair of stiffening elements 30.
One lower edge of blade 28 engages the stencil screen
S (Fig. 3) when the squeegee subassembly is in its
lowered position, and is elevated to a position spaced
above the stencil screen when the squeegee subassembly is
elevated.
Suspended immediately behind the transverse
squeegee subassembly, relative to the direction of the
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1 stencil movement during the stencilling stroke (see Fig. 3),
is a special flow coater - ink scoop subassembly 36. This
unique subassembly is mounted independently of the squeegee,
and is coaxial with the cylinder and offset from its crest.
It includes an elongated, transversely oriented ~relative to
the direction of screen movement) support beam 38 suspended
by a pair of pads 40 on the opposite ends thereof to the
stencil press frame subassembly 12. Depending from the
opposite ends of support beam 38, generally adjacent the
ends of cylinder 14, is a pair of depending trunions 44
having aligned bearing pins 46 ~Fig. 3) therethrough and
through the end plates of a special L-shaped scoop 50, to
pivotally support the scoop thereon. Thus the pivot axis is
between the panels 50a and 50b, offset from their juncture.
Scoop 50 is shown to have an L-shape basically like that of
a piece of angle iron, being formed of two elongated walls
or panels 50a and 50b generally normal to each other and
forming a trough or cavity therebetween, the ends of which
are closed by the end walls 50c (Fig. 4). This scoop can be
rotationally shifted between two positions, serving as a
flow coater in one position for use during the printing
stroke, as a fluid retainer in the second position for use
during the return stroke, and as a scooping member when
shifted from the one to the second position. More specifi-
cally, in the first position, panel 50b is oriented down-
wardly and toward the oncoming stencil screen S during the
stencilling stroke (Fig. 3) with its lower edge 50d being
spaced a controlled fraction of an inch measured in thou-
sandths from the upper surface of the stencil screen to
effectuate a flow-coating action between it and the screen.
In this position, the cavity of the scoop will face lat-
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1 erally, forwardly toward the squeegee and the oncoming
screen to pushingly advance excess stencilling fluid ahead
of it.
In the second position, the scoop has both of its
walls 50a and 50b oriented generally diagonally upwardly
(Fig. 6) to thereby have its cavity upwardly to retain
stencilling fluid therein as a vessel. The scoop performs a
special scooping action in shifting from the first position
to the second position as will be described.
This scoop is moved between these two positions by
a fluid cylinder 60 having its upper end mounted on a
bracket 62 fixed to one of the pads 40, the piston rod 64 of
cylinder 60 being connected by a collar 66 to a crank 68
fixed to one of pins 46. Thus, extension of cylinder 60
shifts scoop 50 from its vertical, ink-retaining orientation
(Fig. 6) to its forwardly facing, flow coating, open posi-
tion (Figs. 3 and 5), while retraction of cylinder 60 shifts
the scoop from its flow coating condition, through the
scooping motion to its fluid retaining condition. This
latter shifting action is caused to occur in a special
fashion so as to scoop up excess ink ahead of the scoop and
flow coating member. More specifically, the scoop 50 is
shifted from its flow coating forwardly oriented position to
its fluid retaining vertical position while the stencil
screen is still in motion and after the squeegee blade is
lifted, causing not only the excess stencilling fluid
immediately ahead of the scoop to be scooped up but also the
excess ink ahead of the squeegee blade~ for retention of the
fluid on the return stroke when the scoop is elevated above
the stencil screen. This will be understood even more
clearly from the further detailed description of the opera-
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1 tion set forth hereinafter.
To employ the concept herein, a stencil screen S
having the desired pattern is mounted in a stencil frame 17
and supported on the traveling reciprocating carriage of
conventional type. The screen and frame are interconnected
with gear racks 18 for reciprocation thereof by arcuate
movement of ring gear 16 which is coaxial with cylinder 14,
simultaneously with rotation of cylinder 14 by this gear.
Thus, relative movement is caused to occur between the
stencil screen and the squeegee and support cylinder, by
advancing the screen between the squeegee and cylinder while
web stock is advanced with the cylinder. This squeegee is
positioned basically above the crest of the cylinder so that
the squeegee forces a previously coated layer of stencilling
fluid from the upper surface of stencil S through the
pattern stencil openings onto underlying web or sheet stock
supported on cylinder 14 (Fig. 3). Immediately behind the
squeegee, relative to the direction of the screen and stock
movement, is the forwardly facing scoop 50 having an excess
of stencilling fluid in front of it (Fig. 5), with a small
portion of this fluid being allowed to flow onto and coat
the passing screen beneath the lower edge 50d spaced a
controlled fraction of an inch above the screen. During the
stencilling stroke, some excess fluid will gather ahead of
the squeegee blade as depicted on the left portion of Fig.
5. Toward the end of the printing stroke, the squeegee
subassembly 20 is elevated as illustrated by the phantom
lines in Fig. 5 to lift the blade 28 from the stencil, while
the stencil screen continues to advance. This continued
screen movement causes the excess fluid previously ahead of
the squeegee blade to encounter the forwardly facing scoop
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1 50. At this time, cylinder 60 is actuated to retract while
screen S is still moving, causing the scoop to be rotated to
cause its leading edge 50d of wall 50b to move basically
beneath the excess fluid and scoop it into the scoop cavity
which is then given a vertical orientation (Fig. 6) to
retain this fluid as a vessel. Repeating this action after
each stencilling stroke prevents significant accumulation of
excess fluid at the end of the stencil screen, a factor with
significant consequences in normal printing operations.
During the return stroke of the screen, the fluid is re-
tained in the upwardly oriented scoop which is spaced above
the screen. On this return stroke, the stencil screen S
will be out of engagement with the print stock due to
elevation of the squeegee. Thus, the stencil screen is
returned to its original position for a repeat stroke
without smearing the ink on the print stock or engaging the
scoop or squeegee blade.
With this relatively simple device, multiple
functions are achieved in a manner to allow flow coating
directly behincl the printing squeegee during the stencilling
stroke, to prevent significant accumulation of excess
stencilling fluid at one end of the stencil screen, to
transport excess fluid back to the leading edge of the
stencil each stroke, and several other advantages and
features readily apparent. It is conceivable that the
specific preferred exemplary embodiment shown may be mod-
ified in various ways to suit a particular situation while
accomplishing the same basic results. For example, the
scoop may have a U or V configuration rather than an L-
shape, the actuator can be electrical, e.g. a solenoid, or
mechanical, e.g. a linkage, rather than a fluid actuator,
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1 and the like. Thus, the invention is intended to be limited
only by the scope of the appended claims and the reasonable
equivalents thereto.
